SAO PAULO – President Dilma Rousseff and Aecio Neves, her challenger in a tight election contest, engaged in a bare-knuckle debate that saw the pair trade accusations of corruption and fiercely argue over who could rekindle Brazil's economy.

The debate Tuesday night was the first in the runoff round that culminates Oct. 26 when upward of 140 million Brazilians are expected to go to the polls and decide who'll be the next leader of the globe's fifth most populous nation and Latin America's biggest economy.

Opinion polls say voters are evenly split and the election is expected to be close to the end.

Rousseff is looking to expand her strong lead among Brazil's poorest voters, while Neves hopes to tap into widespread voter discontent and demands for change seen during huge anti-government protests across the country last year.

Neves, a center-right, business-friendly candidate, attacked Rousseff's economic record and focused on a growing kickback scandal at the state-run oil company Petrobras.

Brazil's growth has slowed since 2010 and the economy went into a recession earlier this year, while there are near-daily revelations about the alleged multimillion-dollar corruption scandal involving top figures at Petrobras, one of whom has said Rousseff's Workers' Party benefited from the scheme.

"I've spent my entire life combatting corruption," Rousseff shot back after Neves read off a litany of accusations.

The leader noted that she has gone after those accused of corruption in her own government, forcing out several Cabinet ministers at the beginning of her term after they faced accusations of wrongdoing.

Rousseff then aired her own list of accusations against her challenger and his Social Democracy Party, citing cases in which Neves favored family members in airport projects while he was governor in Minas Gerais and citing a 16-year-old allegation of a money-laundering scheme that benefited the then head of Neves' party.

Neves responded by telling Rousseff that "I'm going to respond looking into your eyes — you're being irresponsible, candidate, irresponsible!" He accused her of running a "campaign full of lies," which sparked cheers from his supporters in the audience.

Rousseff and Neves represent the two titan parties of Brazilian democracy. The Workers' Party has held the presidency since Jan. 1, 2003, while Neves' party had the office for eight years before that.

In the nearly 12 years the Workers' Party has been in power, Brazil has seen transformative growth and created immense and widely applauded social programs that have lifted millions from poverty and pushed even more into a numerous, if modest, middle class.

Neves argues it was his party that laid the basis for Brazil's advances, implementing the Real Plan that created a new currency, ended years of hyperinflation and sold off money-losing state enterprises, helping modernize Brazil's economy.

Neves made a surprising comeback in the Oct. 5 first-round election, surpassing former environment minister Marina Silva to win the second-highest number of votes. That put him into the runoff with Rousseff, who didn't get the outright majority needed to avoid a second ballot.

In the first round, Rousseff won 42 percent of the vote against Neves' 34 percent.

Neves wants to shrink the government's role in Brazil's economy and open the country to more trade, particularly with the U.S. and Europe. Rousseff has expanded the state's reach and role in the economy with large infrastructure programs and she maintains trade barriers to protect fledgling Brazilian industry.

Rousseff's ad campaign is warning lower middle class and poor Brazilians that the tenuous economic gains they've made in recent years would disappear under a Neves government.

Neves, a former two-term governor in Brazil's second-biggest state who left office in 2010 with a 92 percent approval rating, strongly denies he would cut the popular social welfare programs.

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Associated Press writer Adriana Gomez Licon reported this story in Sao Paulo and Brad Brooks reported from Rio de Janeiro.